PROJECT SUMMARY Over the last decade, the use of post-acute care (PAC) has experienced a rapid growth. Unfortunately, there is a paucity of knowledge about the comparative effectiveness and quality of alternative PAC services needed to make informed clinical and policy decisions. Factors that contribute to this gap in knowledge include the diversity in PAC settings (each with its own set of regulatory and payment incentives, its own treatment approach, and its own patient assessment tool), and heterogeneity in the response of patients to specific treatments that hinder comparisons across settings. The overarching goal is to examine PAC utilization and patient outcomes across different conditions and PAC settings to address important gaps in knowledge that hinder the design of current policy efforts undertaken under the Affordable Care Act (ACA) like episode-based bundling of payments and the creation of Accountable Care Organizations, aimed at improving the value of post-acute care. The objective in pursuit of this goal is to do a comparative cost efficiency study to determine what PAC setting (in isolation or combined with others) delivers the best outcomes, and to what is the relative importance of patient, market and provider factors on the election of setting and the outcomes. Our underlying hypothesis is that specialization in PAC markets with a larger variety of PAC settings leads to improved outcomes (at least for some patient subgroups) but it promotes discontinuities of care that lead to increased utilization. The proposed study will link Medicare claims data and SNF, IRF and HHA assessment data across the 2007-2016 ten-year period to examine PAC outcomes overall and for patients with five tracer conditions: hip fracture, lower extremity joint replacement, CHF, COPD, and stroke. The expected outcomes of our proposed aims are a deeper understanding of how availability, market and provider characteristics impact PAC utilization patterns and patient outcomes. This knowledge has the potential for informing current and future PAC policies intended to reduce/contain overall PAC costs without negatively impacting outcomes.